generating a java client with OAuth2 client_credentials flow support

Description

When I generate the java client for -library=resttemplate, I can inject the OAUth2 resttemplate into the generated ApiClient, and do not need to worry about the dealing with the tokens.
When I generate the java client with no libraries (and the swagger file of the API contains the relevant section for OAuth securityScheme, including the tokenUrl), the generated ApiClient does not include any logic of OAuth flow. The api is secured with ClientCredentials grant.

The only reference the generated ApiClient has to Auth is:
`

   // Setup authentications (key: authentication name, value: authentication).

    authentications = new HashMap<String, Authentication>();

    authentications.put("oauth", new OAuth());`

Swagger-codegen version

2.3.1

Swagger declaration file content or url

{

            "swagger":"2.0",

            "info":{

                            "description":"This API provides account and transaction operations. DEMO",

                            "version":"1.0.0",

                            "title":"Accounts REST API",

                            "termsOfService":"Terms of service",

                            "contact":{},"license":{

                                            "name":"MIT","url":"MIT_LICENSE_URL"}

                            },

            "securityDefinitions": {

    "oauth": {

        "type": "oauth2",

        "tokenUrl": "https://kuku.muku.buku:1234/token",

        "flow": "application",

                                            "scopes": {

                                                            "read": "read all"

                                            }

    }

},

            "security": [

                            {              "oauth": ["read"] }

            ],



            "host":"kuku.muku.buku.chmuku","basePath":"/",

            "tags":

            [{

                            "name":"transaction-controller",

                            "description":"Transaction Controller"

            },

            {

                            "name":"account-controller",

                            "description":"Account Controller"

            }

            ],

            "paths":

            {

            "/accounts":

            {"get":{"tags":["account-controller"],"summary":"findByName","operationId":"findByNameUsingGET","consumes":["application/json"],"produces":["*/*"],"parameters":[{"name":"name","in":"query","description":"name","required":false,"type":"string"}],"responses":{"200":{"description":"OK","schema":{"type":"array","items":{"$ref":"#/definitions/Account"}}},"401":{"description":"Unauthorized"},"403":{"description":"Forbidden"},"404":{"description":"Not Found"}}},"post":{"tags":["account-controller"],"summary":"createAccount","operationId":"createAccountUsingPOST","consumes":["application/json"],"produces":["*/*"],"parameters":[{"in":"body","name":"account","description":"account","required":true,"schema":{"$ref":"#/definitions/Account"}}],"responses":{"200":{"description":"OK","schema":{"type":"string"}},"201":{"description":"Created"},"401":{"description":"Unauthorized"},"403":{"description":"Forbidden"},"404":{"description":"Not Found"}}},"put":{"tags":["account-controller"],"summary":"updateAccount","operationId":"updateAccountUsingPUT","consumes":["application/json"],"produces":["*/*"],"parameters":[{"in":"body","name":"account","description":"account","required":true,"schema":{"$ref":"#/definitions/Account"}}],"responses":{"200":{"description":"OK","schema":{"type":"string"}},"201":{"description":"Created"},"401":{"description":"Unauthorized"},"403":{"description":"Forbidden"},"404":{"description":"Not Found"}}}},"/accounts/transactions":{"get":{"tags":["transaction-controller"],"summary":"findAll","operationId":"findAllUsingGET","consumes":["application/json"],"produces":["*/*"],"responses":{"200":{"description":"OK","schema":{"type":"array","items":{"$ref":"#/definitions/TransactionDTO"}}},"401":{"description":"Unauthorized"},"403":{"description":"Forbidden"},"404":{"description":"Not Found"}}},"post":{"tags":["transaction-controller"],"summary":"makeTransaction","operationId":"makeTransactionUsingPOST","consumes":["application/json"],"produces":["*/*"],"parameters":[{"in":"body","name":"transactionDTO","description":"transactionDTO","required":true,"schema":{"$ref":"#/definitions/TransactionDTO"}}],"responses":{"200":{"description":"OK","schema":{"type":"array","items":{"$ref":"#/definitions/TransactionDTO"}}},"201":{"description":"Created"},"401":{"description":"Unauthorized"},"403":{"description":"Forbidden"},"404":{"description":"Not Found"}}}},"/accounts/transactions/{transactionId}":{"get":{"tags":["transaction-controller"],"summary":"findById","operationId":"findByIdUsingGET_1","consumes":["application/json"],"produces":["*/*"],"parameters":[{"name":"transactionId","in":"path","description":"transactionId","required":true,"type":"string"}],"responses":{"200":{"description":"OK","schema":{"$ref":"#/definitions/TransactionDTO"}},"401":{"description":"Unauthorized"},"403":{"description":"Forbidden"},"404":{"description":"Not Found"}}}},"/accounts/{accountId}":{"get":{"tags":["account-controller"],"summary":"findById","operationId":"findByIdUsingGET","consumes":["application/json"],"produces":["*/*"],"parameters":[{"name":"accountId","in":"path","description":"accountId","required":true,"type":"integer","format":"int32"}],"responses":{"200":{"description":"OK","schema":{"$ref":"#/definitions/Account"}},"401":{"description":"Unauthorized"},"403":{"description":"Forbidden"},"404":{"description":"Not Found"}}},"delete":{"tags":["account-controller"],"summary":"deleteAccount","operationId":"deleteAccountUsingDELETE","consumes":["application/json"],"produces":["*/*"],"parameters":[{"name":"accountId","in":"path","description":"accountId","required":true,"type":"integer","format":"int32"}],"responses":{"200":{"description":"OK","schema":{"$ref":"#/definitions/Account"}},"204":{"description":"No Content"},"401":{"description":"Unauthorized"},"403":{"description":"Forbidden"}}}},"/accounts/{accountId}/transactions":{"get":{"tags":["transaction-controller"],"summary":"findByAccount","operationId":"findByAccountUsingGET","consumes":["application/json"],"produces":["*/*"],"parameters":[{"name":"accountId","in":"path","description":"accountId","required":true,"type":"integer","format":"int32"}],"responses":{"200":{"description":"OK","schema":{"type":"array","items":{"$ref":"#/definitions/TransactionDTO"}}},"401":{"description":"Unauthorized"},"403":{"description":"Forbidden"},"404":{"description":"Not Found"}}}}},"definitions":{"Account":{"type":"object","properties":{"address":{"type":"string"},"balance":{"type":"number"},"creationDate":{"type":"string","format":"date-time"},"email":{"type":"string"},"fullName":{"type":"string"},"id":{"type":"integer","format":"int32"},"userId":{"type":"string"}}},"TransactionDTO":{"type":"object","properties":{"amount":{"type":"number"},"date":{"type":"string","format":"date-time"},"description":{"type":"string"},"fromAccountId":{"type":"integer","format":"int32"},"id":{"type":"string"},"toAccountId":{"type":"integer","format":"int32"}}}}}

Command line used for generation

java -jar swagger-codegen-cli-2.3.1.jar generate -l java -o AccountServiceClientOauth -i
swagger.json --group-id com.infra.samples --artifact-id account-service-client-oauth

Start with the swagger.json securityDefinitions and the Java client generated by the stated swagger-codegen CLI command, especially its ApiClient and OAuth authentication references. Compare this output with generation using -library=resttemplate; done means the no-library Java client handles the declared OAuth2 application/client_credentials flow rather than only exposing an OAuth object.